This invention relates to the powder-metallurgy of brass and in particular, it is concerned with brass powders of novel composition which, when processed by normal powder-metallurgy fabrication techniques, exhibit improved mechanical properties.
Brasses of various compositions are known to be readily adaptable to powder-metallurgical processing techniques. These brasses when produced as brass powders by air atomization or other known techniques and then compacted under pressures of 20-50 tons per square inch (tsi) and sintered at temperatures of 800.degree.-950.degree. C. develop commercially useful tensile properties. While conventional brass powders are firmly established commercially, the properties exhibited thereby are inferior to those obtained in comparable cast or wrought brasses. Consequently, brass powder-metallurgy parts are typically not used in highly stressed structural applications.
Increased strength and hardness of powder-metallurgy fabrications can be attained by increasing the compacting pressure, re-pressing and re-sintering, and/or increasing the sintering temperature. However, the upper limit of compacting pressure is normally considered to be about 50 tons per square inch, since any increase above this pressure substantially raises equipment and tooling costs. Increasing the sintering temperature beyond certain limits is not practicable because blistering may result from the pressure of entrapped gases. Similarly, changes in fabrication techniques are generally considered unacceptable in view of the higher costs involved.
Accordingly representative objects of the present invention are to provide improved brass powder-metallurgical compositions, compacts produced therefrom which exhibit improved mechanical properties, and methods of producing same, all of which are commercially useful and economically practicable.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the composition and product possessing the features, properties, and the relation of components, which are exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.